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Alan Johnston, Derek H. Arnold, Shin'ya Nishida; Spatially localised distortions of perceived duration. Journal of Vision 2005;5(8):765. doi: 10.1167/5.8.765.
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© ARVO (1962-2015); The Authors (2016-present)
We investigated whether the apparent duration of a flickering test pattern can be modified locally through adaptation to flicker (Johnston, Arnold & Nishida (2003) Perception, 32, Suppl. 46–47). Subjects judged the durations of intervals containing 10 Hz sinusoidal modulation of spatially localised 2D Gaussian profile luminance blobs (s.d.: 1.15 deg of visual angle). The adaptation stimulus was either 5Hz or 20Hz Gaussian flicker, centred 9.2 deg to the left or right of fixation. Adaptation was followed by two consecutive test intervals with test stimuli being shown on both the adapted and unadapted side. The order of presentation was randomised. Subjects reported which of the two appeared to last longer. The duration for one 10Hz stimulus was fixed (250, 500 or 750ms) while the other was varied systematically (Standard duration +/− 60%) to measure a psychometric function. The point of subjective equality provided a measure of perceived duration after adaptation. We found that perceived duration decreased after 20Hz with little change after 5Hz adaptation. The duration aftereffect was not a consequence of changes in apparent temporal frequency as it remained when test and standard were matched in temporal frequency. Adaptation to oscillating motion of drifting (20 Hz) sine gratings also reduced apparent duration for test gratings (10 Hz) that were either parallel or orthogonal to the adapting grating and consequently less subject to contrast adaptation. The findings implicate the spatially localised temporal mechanisms of early visual processing in duration encoding for the subsecond range.
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